Magnetic compass



Oct. 17, 1950 L. WOLFE 2,525,848

MAGNETIC COMPASS Original Filed May 16, 1944 In vanfor Lesfer Wolfe A Home Patented Oct. 1 7, 195i) 2,525,848 UNITED STATES PATENT OFFICE MAGNETIC COMPASS Lester Wolfe, Harbourton, N. J. Original application May 16, 1944, Serial No. 535,801. Divided and this application January 10, 1946, Serial No. 640,291

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 2 Claims.

This invention relates to damped magnetic compasses, and in particular to means for varying the damping of eddy current damped compasses, this application being a division of my earlier application for Magnetic Compass, filed May 16, 1944, Serial No. 535,801, which became Patent No. 2,446,568.

It is therefore the primary object of thi invention to provide means for varying the damping characteristics of eddy current damped magnetic compasses.

Other objects will become apparent as the description proceeds in connection with the attached drawings, in which:

Fig. l is a side elevation of an embodiment proximity of the magnetic elements to the conducting damping cup;

Fig. 2 is a sectional view substantially along the line 22 of Fig. 1, looking in the direction of the arrows;

Fig. 3 is a side elevation in section of an embodiment wherein the damping is varied by varying the size or length of a gap in the conducting damping cup; and

Fig. 4 is a side elevation in section of an embodiment wherein variable damping is accomplished by moving the damping cup with relation to the magnetic elements of the damping cup.

Figs. 1, 2 and 4 showembodiments of the invention which relate generally to the preferred embodiment and whichare described in greater detail in my patent hereinabove mentioned.

Fig. 3 illustrates my preferred method and means for obtaining a variation in the eddy current damping effect. In this case the variation is accomplished by changing the conductance of the metallic damping cup. A base 2| of nonconducting material is fastened at its periphery to the bottom edge of the cup-shaped transparent cover 22, A pivot 23 having a resilient mounting in a top and side reading compass card 24 rests upon a V bearing in the top of a central post 25 upstanding from the base 2|. A hemispherical shaped copper cup 38 having an open bottom and top has its open bottom bolted or otherwise fastened to the non-conducting base 2|. "A magnetic system comprising e1ements 39,"40 and 4| is fastened to the compass card and located in the same plane, both within and outside the bowl. A second similar set of elements, horizontally spaced and parallel to the elements 39 to 4| are not shown in the sectional view of Fig. 3. As described in my parent application it is preferred that the central element 40 be of magnetized high coercive force material, and 39 and 4| be of material having a high permeability, to reduce the weight of the card,

Within the base 2| and extendin downwards from the bottom edge of the cup 38 is a cylindrical cavity 42 in axial alignment with the cup and post 25. A disc shaped copper element 43 is axially movable towards and away from the bottom edge of the cup 33 and within. the cavity. At its uppermost position the disc contacts the bottom edge of the cup, thus forming a bridging element. Axial movement of the disc is accomplished by turning a knurled knob 44 on the outer end of a machine screw 4-5 fastened to the disc 43 and threaded through the bottom of the base 2|. Lubber lines 66 and 41 are fastened to the base at. points 180 degrees apart and are curved to lie in close proximity to the compass card. In the embodiment illustrated, the maximum damping effect is obtained when the disc 43 is in its'u permost position and contacting the bot tom edge of the cup because then the conductance of the cup and disc is greatest. As the disc is moved downwards from the cup the gap between it and the cup increases and the conductance of the cup and disc decreases.

It will be understood that the above description and accompanying drawing comprehend only the general and preferred embodiment of the invention and that various changes in construction, proportion and arrangement of the parts may be made within the scope of the appended claims without sacrificing any of'the advantages of the invention.

The invention described herein may be manuconducting material adjacent an end of said rod;

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,003,179 Faus May 28, 1935 2,127,878 .Martin Aug. 23, 1938 Krasnow et a1 June 25. 19 16 

